Impeller pump with reciprocating vane and non-circular rotor

ABSTRACT

An impeller-type pump includes a housing with an internal chamber, a rotor within the chamber and a vane mounted to the housing for reciprocating action such that an end of the vane contacts the rotor and effectively divides the chamber between induction and exhaustion rotor chambers. The rotor has a non-circular cross-sectional configuration, such that its outside surface forms a camming surface that drives the vane in a reciprocating fashion upon rototation of the rotor. The rotor may be oval in cross section or have a complex cross-sectional configuration with a substantially flat trailing face forming a stop to prevent reverse direction rotation, and a curved leading face which forms a cam surface to elevate the vane upon rotation of the rotor.

BACKGROUND OF THE INVENTION

The present invention relates to an impeller or rotary pump, of the type comprising a housing (the “stator” portion of the pump) with an internal rotor and displaceable vanes located between the rotor and the rotor chamber wall for separating the induction and exhaustion or expulsion regions of the rotor chamber. Rotor rotation has the effect of continuously drawing fluid through the pump as the fluid sequentially passes through the induction and exhaustion regions. These regions are effectively formed on a continuous basis in the space between the rotor surface and the chamber wall between a fluid inlet and a fluid outlet. Arrangements of this type comprise positive displacement pumps, wherein each cycle of rotation displaces a substantially constant fluid volume regardless of inlet and outlet pressure, apart from the usually minor effects of fluid compression under pressure. Pumps of this type may be used for pumping fluid having a wide range of viscosities, ranging from gasses to relatively viscous liquids such as heavy oils and greases. The relative simplicity of such pumps makes them desirable for a wide range of applications, including all manner of industrial, commercial, marine, medical, and other uses. As well, with suitable modifications such pumps may be converted into turbines, wherein a pressure differential between fluid bodies may be converted into mechanical energy.

Rotary vane-type pumps, which employ an internal rotor or impeller to drive a fluid, are known both for use as pumps and turbines. For example, the present inventor's previous U.S. Pat. No. 6,554,596 describes a rotary device having a plurality of vanes, wherein the stator includes a fluid inlet and outlet with an internal generally cylindrical bore. A rotor is mounted eccentrically within the bore (the axis of the rotor being displaced from the central axis of the bore), with a plurality of vanes extending radially outwardly from the rotor to provide a sealing contact between the internal bore surface and the rotor. This device may be used as a turbine to convert the energy of a flowing fluid into mechanical energy. Other arrangements are known, in which a rotor is eccentrically mounted within a bore, with a plurality of vanes extending from the exterior surface of the rotor for reciprocating movement relative to the rotor. Rotation of the rotor draws fluid into the space between the rotor and the inner wall of the bore, with the vanes serving to propel the fluid through the housing and out of the discharge conduit. The combination of the vanes and the eccentric mounting of the rotor provide a one-way flow of the fluid and effectively separates the chamber into a plurality of induction and exhaustion chambers.

It is an object of the present invention to provide an improved vane-type rotary pump suitable for use with a range of fluid viscosities and which is relatively simple and inexpensive in its construction.

SUMMARY OF THE INVENTION

In one aspect, the present invention comprises a rotary vane pump comprised of the following elements:

-   -   a stator, consisting of a stationary pump housing having, in         sequential fluid communication with each other, a fluid inlet, a         fluid outlet, and an internal pump chamber or bore having a         cylindrical region;     -   a cam-shaped rotor mounted for rotation within the cylindrical         region of the pump chamber, the rotor having a central axis of         rotation and a non-cylindrical exterior cam surface for contact         with the fluid being pumped. The rotor shape preferably         comprises first substantially opposed portions each having an         equal radius such that these opposed portions each form a         sealing contact with the inside surface of the housing bore, and         second rotor portions (which may also be substantially opposed         to each other) having a reduced radius to form a space between         the rotor surface and the inside surface of the rotor bore for         receiving a volume of fluid for passage through the pump upon         rotation of the rotor. The said spaces effectively form         induction and exhaustion regions upon rotation of the rotor;

a drive means for rotatably driving the rotor, said drive means comprising any convenient means for rotatably driving the rotor, including without limitation any type of motor, whether or not in direct mechanical linkage with said rotor. The drive means may comprise a fluid flow through said pump in the case of the pump being used as a turbine; and

-   -   at least one vane mounted to the housing and extending into the         pump chamber. Preferably, only a single vane is provided         although multiple vanes are contemplated. The vane is mounted         for reciprocating motion relative to the housing and has a         contact surface for contacting the cam surface of the rotor,         such that the vane effectively divides the pump chamber into two         regions on opposing sides of the vane during the phase of the         rotor rotation when the cam surface thereof is not in contact         with the chamber wall at the position of the vane. Each region         on either side of the vane is defined by the space between the         rotor surface and the chamber wall. A first region effectively         forms an induction chamber and a second region forms an         exhaustion chamber, such that fluid separation is maintained         between the inlet and outlet. The contact between the vane and         the cam surface of the rotor results in rotation of the rotor         driving the vane in a reciprocating motion.

The rotor may comprise various cross-sectional configurations, including being essentially or generally oval-shaped in section. Alternatively, the rotor may have a shape composed of opposing arms, each arm having a curved leading cam surface for elevating the vane upon rotation of the rotor and a trailing flat or substantially flat surface, such that the trailing surface effectively forms a stop member for abutting against the reciprocating vane to prevent reverse-direction rotation of the rotor. This configuration also increases the effective chamber volume, since only a single side of each rotor arm, the leading face, need be bowed outwardly. Other rotor configurations are possible within the scope of the invention.

The central axis of the vane (i.e. the central plane defining the middle of the vane) may be aligned with the axis of rotation of the rotor or displaced relative thereto, for example when used with the type of rotor configuration described above having a flat trailing surface. Preferably, biasing means are provided for biasing the vane against the cam surface, for example (but not limited to) a spring or other member having a similar function. The differential pressure between pump inlet and outlet may also be harnessed to drive the vanes. Thus, a conduit may be provided from the pump outlet (having a higher pressure fluid) into the vane housing where up expansion of the fluid drives the vane towards the rotor. The vane may be housed within a slot or track within the housing. The contact surface of the vane may include an elongate roller bearing or other low-friction surface to minimize friction between the vane and the cam surface of the rotor. The vane is preferably a flat panel-like member and is optionally provided with a broadened portion at its lower edge where it contacts the rotor, such as bulbous region extending laterally outwardly from one or both sides of the vane.

It will be further seen that the invention may be fabricated from any suitable material or combination of materials, including various metals and plastics suitable for the demands of the pump environment. As well, the pump may be provided either in isolation or as a component of another device.

These and other features of the present invention will now be further illustrated by way of a detailed description of an embodiment of the invention, which is not intended to limit the scope of the invention.

In the present specification, including the claims, various directional references are made such as upper, lower, vertical, horizontal, etc. These are intended merely for convenience of description and are not intended to limit the scope of the invention in any respect. It will be readily seen by persons skilled in the art that the present invention may be oriented in any position. Further, a degree of departure is permitted from strictly vertical, horizontal, and similar directional references.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other advantages of the invention will become apparent upon reading the following detailed description and upon referring to the drawings in which:

FIG. 1 is a schematic view, in cross-section, of a first embodiment of the invention;

FIGS. 2 a through 2 h are schematic cross-sectional views of the first embodiment, illustrating sequential positions of the rotor and reciprocating vane to illustrate the pump cycle;

FIG. 3 is a perspective view of the vane portion of the first embodiment;

FIG. 4 is a schematic side elevational view of the vane portion of the first embodiment, the broken lines indicating hidden parts;

FIG. 5 is a schematic cross-sectional view of a second embodiment of the invention;

FIG. 6 is a schematic perspective view, partly in section, of the second embodiment;

FIG. 7 is a further perspective schematic view, partly in section, of the second embodiment;

FIG. 8 is a further perspective view of the vane portion of the second embodiment;

FIG. 9 is a still further perspective view of the vane portion of the second embodiment.

FIG. 10 is a schematic side elevational view of the vane portion of the second embodiment, the broken lines indicating hidden parts;

FIG. 11 is a schematic perspective view of the vane portion of the second embodiment;

FIG. 12 is a schematic perspective view of a third embodiment of the invention; and

FIG. 13 is a perspective view of the exterior of the third embodiment.

While the invention will be described in conjunction with the illustrated embodiments, it will be understood that it is not intended to limit the invention to such embodiments. On the contrary, it is intended to cover all alternatives, modifications and equivalents as may be included within the scope of the invention as defined by the appended claims.

DETAILED DESCRIPTION OF THE INVENTION

In the following description, part numbers have been assigned, with similar or corresponding parts in the separate embodiments being assigned the same number for convenience of description.

The example described herein of the positive displacement vane-type pump 10 of the present invention comprises in general a static pump housing 12 having an internal chamber or bore 14, for housing a rotor 20 and reciprocating vane 22. Turning first to the embodiment illustrated in FIGS. 1 through 4, the pump housing 12 includes a fluid inlet 30 and a fluid outlet 32. It will be seen that the relative dimensions of these and other components of the pump are presented merely by way of illustration and may be varied within a wide range according to the specific pump requirements. Such alterations and modifications are within the skill and knowledge of persons skilled in the art. The housing 12 includes a bore 14 for housing the rotor 20, the bore 14 having a lower portion 34 which is cylindrical, the inner surface 36 of which provides a smooth contact surface for the rotor 20. The rotor bore 14 includes opposed lateral side walls 38, which as is described below, conform to the end walls 39 of the rotor 20 (parts 38 and 39 being visible in FIGS. 6 and 7). The inlet 30, rotor bore 14, and outlet 32 are all in sequential fluid communication with each other. That is, at any given point during the pump cycle, fluid communication between the inlet 30 and outlet 32 is blocked by the combination of the rotor 20 and vane 22 in contact with each other and the inner surface 36 of the bore 14, as will be described in detail below. Thus, the inlet and outlet are in fluid communication with each other to the extent that fluid entering the inlet passes sequentially through inlet, the rotor bore and the outlet during operation of the pump 10.

The housing 12 includes a block 40 for receiving and supporting the reciprocating vane 22. The block includes a vertical channel 42 for housing the vane, with the channel 42 having flat lateral sides for contact with the corresponding faces of the vane 22. The exterior of the vane block 40 protrudes upwardly from the pump to provide sufficient interior space within the block to accommodate the vane 22 when in the retracted position. A screw-threaded opening 44 extends through the upper surface of the block to the pump exterior and communicates with the interior of the channel 42. A spring tension adjustment screw 46 is threaded through the opening and protrudes into the upper end of the channel. A spring 48 is housed within the channel 42, and biases the vane 22 downwardly against the rotor 20, as will be discussed in more detail below. It will be evident to those skilled in the art that the spring 48 may be replaced by any convenient biasing means, such as, without intending to limit the scope of the invention, a gas spring, a resilient member (such as an elastomeric rod), etc.

Rotor 20 includes a central axle 50 which is journalled for rotation on an axle mount 52, which is not shown but is conventional in design. The axle 50 is operatively connected to a drive for rotating the rotor 20. The drive is not shown, but will be readily seen by those skilled in the art that any convenient drive means may be employed for rotating the axle and, in turn, the rotor. For example, depending on the pump application, there may be used any type of motor, hydraulic drive, or a hand crank for hand operation. As well, as will be described below, the invention may be operated as a turbine wherein an existing pressure differential between the inlet and outlet rotatably drives the rotor 20, in which case no drive means need be provided for the rotor, as the fluid passing through the pump serves as the drive means. The rotor 20 is generally elongate and extends between the side walls 38 of the rotor bore. The opposed end walls 39 of the rotor 20 are flush with the corresponding side walls 38 of the bore 14 and in contact therewith to prevent or minimize fluid leakage. While flat end walls 39 are preferred, it will be seen that the end walls 39 and the corresponding side walls 38 of the bore may have any convenient shape or configuration. The rotor 20 is characterized by a non-cylindrical shape, namely having two opposed (either directly or substantially directly) and equal first radii (a) which define the maximum diameter of the rotor for any given point along its length (e.g. the rotor may be tapered or otherwise shaped along its length). The radii (a) define the outer margin of opposed arms 56 of the rotor and thus define opposed rotor edges 54 for contact with the cylindrical inside surface 36 of the rotor bore 14. The rotor is further defined by opposed or near-opposed radii (b) which define the minimum rotor diameter. It will be seen that the rotor 20 and bore 14 may be tapered or otherwise shaped along their length which result in radii (a) and (b) varying along the rotor length.

In the embodiment of FIGS. 1 to 4, the rotor 20 is comprised of two similar opposing paddles or arms 56 extending from the central axis. The arms 56 each have a curved leading face 60 and an opposed flat trailing face 62. The trailing face 62 of a first paddle 56 merges with the leading face 60 of the opposed paddle 56. A stepped portion 64 characterizes the junction between the trailing face 62 of a first paddle and the leading face 60 of an opposed second paddle, having a downward step from the leading to the trailing faces. The stepped portion 64 includes a rounded exposed edge merging with an angled shoulder 66.

The reciprocating vane 22 according to the first embodiment of the present invention is shown in more detail in FIGS. 3 and 4. The vane 22 is generally planar with flat front and rear faces (although the vane may comprise other configurations such as arcuate in section). The vane 22 is composed of opposed lateral side shoulders 70 which sandwich a central (optionally) recessed panel 72. The side shoulders 70 may be integral with the panel 72 and flush therewith (as will be described in greater particularity with respect to the second embodiment) or the panel 72 may be recessed relative to the side walls, as seen in FIGS. 3 and 4. The vane 22 and channel 42 within the vane block 40 are shaped to provide a snug fit, which is substantially impervious to fluid leakage while still permitting the vane to slide within the channel in a reciprocating fashion. The side shoulder portions 70 of the vane 22 fit within corresponding recesses 74 in housing 12 beside the vane block and aligned with channel 42. Preferably, the upper face 78 of the vane 22 is substantially flat, while the side shoulders 70 extend downwardly past the lower edge of the central panel 72, as seen in inverted view in FIG. 3. The lower edge of the central panel 72 includes a bulbous laterally-extending rounded protrusion 80 defining the lower edge of the central panel 72. The bulbous protrusion 80 provides additional strength to the vane at the point of contact with the rotor. For maintaining a sealing contact with the rotor, an elongate roller bearing 82 is provided at the lower edge of the central panel. The roller bearing 82 fits within a corresponding receiving channel 84 within the vane 22 extending transversely across the lower edge thereof. The bearing 82 may comprise any convenient material, for example stainless steel or Teflon™.

A further feature of the first embodiment is that the vane 22 is positioned within the housing 12 such that it is offset from the axis of rotation of the rotor 20, such that when seen in side view, the central axis of the vane is to the left (downstream side) of the rotor axis. That is, it is offset towards the downstream side of the rotor axis. As will be described below, the shape of the rotor 20 in conjunction with the offset position of the vane 22 permits a one-way operation of the rotor and prevents the rotor from spinning in a reverse direction thereby blocking any countervailing flow from the outlet to the inlet. This shape optimizes the volume of the chamber thus increasing flow rates. The amount of offset of the vane 22 relative to the rotor axis is a function of the rotor thickness, i.e. the vane 22 is displaced from the rotor axis by a horizontal distance (c) which is equal to the horizontal distance between the flat rear face of the rotor and a vertical radius of the rotor 20, when the rotor is in the vertical position. This displacement thus permits the vane 22 to slide downwardly into a position of full contact with the flat side of the rotor, when the rotor is in a vertical position as shown in FIGS. 2F and 2G.

Operation of the first embodiment will now be described by reference to FIGS. 2A through 2H. In a first position shown in FIG. 2A, the rotor 20 is generally horizontal, with the vane 22 in a substantially extended position such that it extends downwardly to contact the rotor 20. Clockwise rotation of the rotor, as shown in FIG. 2B, expands the effective size of the induction portion of the rotor chamber 14, thus drawing fluid into the chamber 14. Continued rotor rotation, as shown in FIGS. 2C through 2E continues to expand the relative size of the induction chamber, while the vane 22 is urged upwardly by contact with the leading face 60 of the rotor 20, until the rotor reaches a substantially vertical position as shown in FIG. 2F. At this point, the flat trailing face 62 of the rotor is aligned with the corresponding face of the vane 22, and the vane thus moves downwardly, on the urging of the internal spring 48. Preferably, the spring tension is adjusted to provide a very rapid downward movement of the vane. The vane is maximally extended at FIG. 2G, with further downward movement of the vane being prevented by contact with the stepped portion 64 of the rotor 20, which protrudes radially outwardly from the flat trailing face 62. It will be seen that when the vane 22 abuts the trailing face 62, the rotor 20 is prevent from rotating in a reverse (counter clockwise) direction.

It will be seen that the trailing face 62 need not be substantially flat in order to achieve solely the objective of increasing the effective volume of the rotor bore 14 if there is no need for the anti-rotation feature. Thus, this feature is provided if trailing face 62 has a flatter surface than leading face 60.

Continued rotation of the rotor, as seen in FIG. 2H, elevates the vane 22 while expelling fluid from the outlet 32 and effectively forming another induction chamber at the fluid inlet.

A second embodiment of the invention is illustrated at FIGS. 5 through 11. In this version, there is shown the inlet 30 and outlet 32 being parallel and protruding from the upper face of the pump 10, although it will be seen that with minor modifications horizontal inlets and outlets as in the first embodiment may be provided, or the inlet and/or outlet being in essentially any position. The rotor 20 of the second embodiment is generally oval and symmetrical in cross-section, and thus may rotate in either direction such that the inlet and outlet conduits may be reversed in function, depending on the direction of rotation of the rotor. The vane 22 (shown with more detail in FIGS. 8 and 9) is generally similar to the vane of the first embodiment but with the bulbous portion 80 at the lower edge region of the vane extending laterally to an equal extent from either side of the vane. As well, the vane 22 may comprise a unitary panel structure (i.e. without protruding side rails) having depending stop members on either side which extend below the lower edge of the vane, as shown more particularly in FIGS. 8 through 11.

In a further aspect of the second embodiment, shown in FIGS. 10 and 11, rather than the biasing means being housed within the vane block 40, the vane itself is provided with spring-loaded push rods 90 which retract into corresponding apertures 92 within the vane. FIGS. 8 and 9 show the vane with the push rods retracted while FIGS. 10 and 11 show the push rods extended. These push rods 90 may be biased to protrude from the vane by any convenient biasing means, including a spring 94 or other resilient member.

The vane block 40 includes a drainage opening or slot 96 communicating with the vane-receiving channel 42, to permit fluid which has leaked into the main channel 42 to drain into the main fluid outlet 32. The slot 96 potentially serves a second function. When oriented such that it opens towards the higher-pressure side of the pump (i.e. the downstream outlet), the slot 96 permits use of the inlet/outlet pressure differential to drive or assist in the driving of the vane 22. Thus, the relatively high pressure fluid stream will enter the channel 42 in the space above the vane. Because this fluid is at a relatively high pressure, it will exert a biasing force against the vane 22 to urge it downwardly against the rotor 20. This effect is enhanced by the provision of partly enclosed inlet and outlet chambers 95 and 97 respectively with the slot 96 opening into the outlet chamber 97.

As seen more particularly in FIG. 7, the vane block 40 only receives an upper portion of the vane 22 therein, with a lower portion of the vane 22 extending downwardly into the main chamber 14.

The lateral side walls of the chamber include opposed track slots aligned with the vane channel, for receiving and guiding the end wall portions of the vanes.

As seen more particularly in FIG. 5, the vane 22 is aligned with the axis of rotation of the rotor 20.

In operation, the second embodiment operates in a similar manner to the first embodiment, although it will be seen that the symmetrical oval shape of the rotor does not provide for an anti-reversal function. The second embodiment has particular use for providing a reversible pump, that is, a pump which is equally capable of discharging the fluid through either conduit by reversing the direction of rotation of the rotor 20.

A third embodiment of the invention is illustrated at FIGS. 12 and 13. This embodiment is similar to the second embodiment, having a generally oval-shaped rotor 20. However, the vane 22 is offset from the axis of rotation of the vane 20, towards the outlet (downstream) side of the vane 22. The offset position of the vane permits it to be more efficiently urged upwardly into its retracted position upon rotation of the rotor 20. A further difference from the second embodiment resides in the shape of the bulbous lower protrusion 80 of the vane, which is similar in shape to the first embodiment. Further, the inlet and outlet regions 30 and 32 respectively are shown in an alternative arrangement, namely being generally horizontally disposed and offset from each other wherein the inlet enters the chamber at an elevated position relative to the outlet.

Although the present invention has been described by way of a detailed description of the invention, including particular embodiments thereof, it will be seen by those skilled in the art that the present invention includes within its scope departures from and variations to the elements particularly described, including omission of inessential elements and addition of additional elements, without departing from the full scope of the invention. In particular, the scope of the invention is defined by the claims appended hereto, as these may be amended from time to time, and including any components, elements, or operation methods which are the functional or mechanical equivalent thereof. 

1. A rotary vane pump comprising: a static pump housing having in sequential fluid communication a fluid inlet, a fluid outlet and a pump chamber having a bore at least a portion of which is circular in section; a rotor mounted for rotation within the circular portion of said bore, said rotor having a central axis of rotation and an exterior camming surface which in section is non-cylindrical; at least one vane mounted within said housing for reciprocating motion relative to said housing between an extended and a retracted position, said vane having a contact surface for sealing contact with said camming surface of said rotor, wherein rotation of said rotor drives said vane in said reciprocating motion; and said vane and rotor maintaining fluid separation between said inlet and said outlet.
 2. A pump as defined in claim 1, further comprising drive means for rotating said rotor.
 3. A pump as defined in claim 1, further comprising biasing means acting between said vane and said housing, to urge said vane against said rotor.
 4. A pump as defined in claim 1, wherein said vane is slidably housed within a channel recessed within said housing and opening into said pump chamber.
 5. A pump as defined in claim 1, comprising a single vane.
 6. A pump as defined in claim 1, wherein said vane is displaced from the axis of rotation of said rotor towards the downstream side of said pump.
 7. A pump as defined in claim 6, wherein said rotor is substantially oval-shaped in cross-section.
 8. A pump as defined in claim 1, wherein said rotor comprises substantially opposed portions having equal radii of maximum length for each contacting the inside surface of said bore with a sliding sealed contact.
 9. A pump as defined in claim 8, wherein said rotor portions each comprise a curved leading face forming a cam surface for elevation of said vane upon rotation of said rotor and a substantially flat trailing face, said vane having a corresponding flat face for contact with said trailing face and said vane being displaced relative to the axis of rotation of said rotor such that each said trailing face of said rotor may fully contact the corresponding flat face of said vane when said vane is in said extended position to prevent reverse rotation of said rotor.
 10. A pump as defined in claim 8, wherein said rotor portions each comprise a curved leading face forming a cam surface and a trailing face having a flatter surface than said leading face.
 11. A pump as defined in claim 1, wherein said vane includes a low-friction contact member for maintaining a sealing contact with said rotor.
 12. A pump as defined in claim 11, wherein said low friction contact member comprises a roller bearing, partly recessed into a channel within said vane.
 13. A pump as defined in claim 11, wherein said vane includes a thickened region extending laterally relative to the contact surface at a region of said vane adjacent to said contact member.
 14. A pump as defined in claim 1, further comprising a drain in communication with said channel, for discharge of fluid from said channel.
 15. A pump as defined in claim 14, wherein said drain opens to said fluid outlet for harnessing the relatively higher fluid pressure therein to urge said vane towards said rotor.
 16. A pump as defined in claim 1, wherein said housing includes lateral side walls, at least one of which includes a slot for receiving and guiding said vane.
 17. A rotary vane pump comprising: a static pump housing having in sequential fluid communication a fluid inlet, a fluid outlet and a pump chamber having a bore at least a portion of which is circular in section; a rotor mounted for rotation within the circular portion of said bore, said rotor having a central axis of rotation and an exterior camming surface which in section is non-cylindrical; at least one vane mounted within said housing for reciprocating motion relative to said housing between an extended and a retracted position, said vane having a contact surface for sealing contact with said camming surface of said rotor, wherein rotation of said rotor drives said vane in said reciprocating motion; and said vane being positioned to maintain fluid separation between said inlet and said outlet; wherein said rotor comprises substantially opposed portions having equal radii of maximum length each for contacting the inside surface of said bore with a sliding sealed contact.
 18. A pump as defined in claim 17, further comprising drive means for rotating said rotor.
 19. A pump as defined in claim 17, further comprising biasing means acting between said vane and said housing, to urge said vane against said rotor.
 20. A pump as defined in claim 17, wherein said vane is slidably housed within a channel recessed within said housing and opening into said pump chamber.
 21. A pump as defined in claim 17, comprising essentially a single vane.
 22. A pump as defined in claim 17, wherein said vane comprises a generally panel-shaped member having a central axis, said axis being displaced from the axis of rotation of said rotor towards the downstream side of said pump.
 23. A pump as defined in claim 22, wherein said rotor is substantially oval-shaped in cross-section.
 24. A pump as defined in claim 17, wherein said rotor comprises opposed portions having equal radii of maximum length for each contacting the inside surface of said bore with a sliding sealed contact.
 25. A pump as defined in claim 24, wherein said rotor portions each comprise a curved leading face forming a cam surface for elevation of said rotor upon rotation of said rotor and a substantially flat trailing face, said vane having a corresponding flat face for contact with said trailing face and said vane being displaced relative to the axis of rotation of said rotor such that each said trailing face of said rotor may fully contact the corresponding flat face of said vane when said vane is in said extended position to prevent reverse rotation of said rotor.
 26. A pump as defined in claim 24, wherein said rotor portions each comprise a curved leading face forming a cam surface and a trailing face having a flatter surface than said leading face.
 27. A pump as defined in claim 17, wherein said vane includes a low-friction contact member for maintaining a sealing contact with said rotor.
 28. A pump as defined in claim 27, wherein said low friction contact member comprises a roller bearing, partly recessed into a channel within said vane.
 29. A pump as defined in claim 27, wherein said vane includes at least one bulbous lateral extension at a region of said vane adjacent to said contact member.
 30. A pump as defined in claim 17, further comprising a drain in communication with said channel, for discharge of fluid from said channel.
 31. A pump as defined in claim 30, wherein said drain opens to said fluid outlet for harnessing the relatively higher fluid pressure therein to urge said vane towards said rotor.
 32. A pump as defined in claim 17, wherein said housing includes lateral side walls, at least one of which includes a slot for receiving and guiding said vane.
 33. A rotary vane pump comprising: a static pump housing having in sequential fluid communication a fluid inlet, a fluid outlet and a pump chamber having a bore at least a portion of which is circular in section; a rotor mounted for rotation within the circular portion of said bore, said rotor having a central axis of rotation and an exterior camming surface which in section is non-cylindrical; at least one vane mounted to said housing for reciprocating motion relative to said housing between an extended and a retracted position, said vane having a contact surface for sealing contact with said camming surface of said rotor, wherein rotation of said rotor drives said vane in said reciprocating motion; and said vane being positioned to maintain fluid separation between said inlet and said outlet; wherein said rotor comprises substantially opposed portions having equal radii of maximum length for each contacting the inside surface of said bore with a sliding sealed contact and said portions each comprise a curved leading face forming a cam surface for elevating said vane upon rotation of said rotor and a substantially flat trailing face, said vane having a corresponding substantially flat face for contact with said trailing face and said vane being displaced relative to the axis of rotation of said rotor such that each said trailing face of said rotor may fully contact the corresponding flat face of said vane when in said extended position to prevent reverse rotation of said rotor.
 34. A pump as defined in claim 33, further comprising drive means for rotating said rotor.
 35. A pump as defined in claim 33, further comprising biasing means acting between said vane and said housing, to urge said vane against said-rotor.
 36. A pump as defined in claim 33, wherein said vane is slidably housed within a channel recessed within said housing and opening into said pump chamber.
 37. A pump as defined in claim 33, comprising essentially a single vane.
 38. A pump as defined in claim 33, wherein said vane comprises a generally panel-shaped member having a central axis, said axis being aligned with the axis of rotation of said rotor.
 39. A pump as defined in claim 38, wherein said rotor is substantially oval-shaped in cross-section.
 40. A pump as defined in claim 33, wherein said rotor comprises substantially opposed portions having equal radii of maximum length for each contacting the inside surface of said bore with a sliding sealed contact.
 41. A pump as defined in claim 33, wherein said vane includes a low-friction contact member for maintaining a sealing contact with said rotor.
 42. A pump as defined in claim 41, wherein said low friction contact member comprises a roller bearing, partly recessed into a channel within said vane.
 43. A pump as defined in claim 41, wherein said vane includes at least one bulbous lateral extension at a region of said vane adjacent to said contact member.
 44. A pump as defined in claim 33, further comprising a drain in communication with said channel, for discharge of fluid from said channel.
 45. A pump as defined in claim 44, wherein said drain opens to said fluid outlet for harnessing the relatively higher fluid pressure therein to urge said vane towards said rotor.
 46. A pump as defined in claim 33, wherein said housing includes lateral side walls, at least one of which includes a slot for receiving and guiding said vane. 